Wind turbines are common in the state of the art and are becoming increasingly more important for generating electrical power on a global scale. The most common wind turbines include horizontal axis wind turbines, in which a rotor hub that bears a plurality of turbine blades is attached to the internal rotor of an electric machine through a horizontal drive shaft and gearbox. The hub is mounted in a gyratory manner onto a nacelle at the top of a tower. The nacelle houses the gearbox, the electric machine and other functional elements. The gearbox, in addition to being fairly expensive, is an element that requires constant maintenance and a great deal of space, hence the dimensions of the nacelle should be sufficiently large enough to house the gearbox.
“Direct drive” wind turbines have been developed to solve this problem. A direct drive wind turbine comprises an external rotor and internal stator, a horizontal shaft connected to the external rotor so that the external rotor turns around the internal stator. It also comprises a nacelle mounted at the top of a tower that houses a shaft, carrier mechanism for bearing the horizontal shaft. The blade roots are connected to the external rotor, generally through a hollow hub. The dimensions of the hub are designed to enable access to some bolts through which the blade root is fastened directly to the hub or, where pertinent, likewise to a pitch angle adjustment mechanism to regulate the blade attack angle. The hub is an additional element that should be connected to the external rotor. The foregoing requires a relatively large unit and entails the need for additional connection elements, which should be mounted and maintained. A direct drive wind turbine of this sort is described, for instance in document WO 01/21956-A1.
Documents EP-0864748-A1, EP1394406A2, EP-1783363-A1 and DE-44155570-A1 also describe direct drive wind turbines that lack a hub with the blades directly coupled to support structures mounted equidistantly on external peripheral parts of the body of an external rotor. The problem inherent in wind turbines of this son involve the bolts employed for fastening the blade or, where pertinent, the pitch mechanism elements, to the blade support structures, since they are not accessible for inspection, maintenance or repair and/or replacement tasks. Thus, when these tasks are necessary, the entire nacelle rotor must be dismounted and lowered to the ground.